1. The Field of the Invention
This invention relates generally to the field of liquid crystal displays (LCD), and more particularly, to a novel LCD device structure and a method of manufacturing the same.
2. Description of the Related Art
An LCD device is indispensable for manufacturing notebook-type personal computers because they are much lighter and thinner than cathode-ray tube (CRT) monitors. In addition, the energy consumption of the LCD device is much lower than that of the CRT monitor.
However, the image quality of the LCD device is normally not as good as that of the CRT monitor. To improve the image quality and to decrease energy consumption, the aperture ratio (the ratio of pixel area to total display area) of the LCD device must be increased as much as possible.
Responding to these needs, a Pixel-on-Passivation (POP) structure is recently employed for a thin-film-transistor liquid-crystal-display (TFT-LCD) device to increase the aperture ratio. In the POP structure, a capacitance between a pixel electrode and bus lines must be kept sufficiently low such that the image quality is not degraded by the signal delay. In order to decrease the capacitance, the dielectric constant of an interlayer insulator between the bus lines and the pixel electrode must be low.
To form an interlayer insulator for the POP structure, several insulating materials such as photo-sensitive resins and dry-etch type resins can be used.
The photo-sensitive resins are widely used because they can be easily patterned using a conventional photolithographic process. However, the dielectric constants of photo-sensitive resins are typically high (ε˜3.8) and are thus not suitable for manufacturing a high-quality LCD device.
In contrast, dry-etch type resins generally have lower dielectric constant and higher transparency. However, the dry-etch type resins are normally photo-insensitive. Therefore, to pattern the dry-etch type resins, a conventional photoresist has to be coated over the dry-etch type resins for photolithographic process steps. A stripping process is then used to remove the photoresist after patterning the dry-etch type resins.
However, an organic stripper that is typically used for the stripping process can severely damage the dry-etch type resins. In addition, some dry-etch type resins have other problems. For example, perfluorocyclobutane (PFCB), developed by Dow chemical, although having very low dielectric constant (ε˜2.35), its adhesion to typical inorganic films, SiNx, TaN or indium tin oxide (ITO), is too poor for proper fabrication of the LCD device. Also, Organic Spin-on-glass (SOG), also having very low dielectric constant (ε˜2.3), tends to have many cracks in a layer of the SOG if its thickness exceeds approximately 1 μm. Also, another problem of the dry-etch type resins is that normally they are much more expensive than typical photo-sensitive resins.
For these reasons, the photo-sensitive resins are still used for manufacturing the LCD device even though the photo-sensitive resins have low dielectric constant that is not good for achieving a high-quality LCD device.
Accordingly, there is a need to develop a method of manufacturing high-resolution LCD devices overcoming the drawbacks of conventional materials. Also, there is a need to develop a method of manufacturing LCD devices with fewer or simplified process steps.